Balanced drive mechanism for large thickeners



April 5, 1960 c. H. SCOTT 2,931,241

BALANCED DRIVE MECHANISM FOR LARGE THICKENERS Filed March 6, 1956 4Sheets-Sheet 1 Fig. I.

INVENTOR.

Charles H. Scott B Y 04/5 If My %TORNEY April 5, 1960 c. H. SCOTT2,931,241

BALANCED DRIVE MECHANISM FOR LARGE THICKENERS Filed March 6, 1956 4Sheets-Sheet 2 44 47 3& p

INVENTOR.

Charles H. Scott Fig. 2.

c. H.' SCOTT 2,931,241

BALANCED DRIVE MECHANISM FORLARGE THICKENERS April 5, 1960 4Sheets-Sheet 3 no 5 9 l I 6 h m a M d e l 1 F C. H. SCOTT April 5, 19602,931,241 BALANCED DRIVE MECHANISM FOR LARGE THICKENERS I Filed March 6,1956 4 Sheets-Sheet 4 INVENTOR.

Chorles H. Scott United States Patent BALANCED DRIVE MECHANISM FOR LARGETHICKENERS Charles H. Scott, South Norwalk, Conn, assignor to Porr-Oliver Incorporated, Stamford, Conn., a corporation of DelawareApplication March 6, 1956, Serial No. 569,933

8 Claims. (Cl. 74-410) This invention relates to settling tanks to whicha feed suspension of solids is admitted, while clarified liquidoverflows at the periphery, and a rotary rake structure conveys settledsolids over the tank bottom to a zone or point of outlet usually at thecenter of the tank; more particularly, this invention relates toimprovements in the power drive mechanism or drive head for the rotarysediment raking structure in such a tank.

This invention relates to settling tanks to which a feed suspension ofsolids is admitted, While clarified liquid overflows at the periphery,and a structure conveys settled solids over the tank bottom to a zone orpoint of outlet usually at the center of the tank.

More particularly, this invention relates to improvements in the powerdrive mechanism or drive head for the rotary rake structure, Where themechanism is of the kind that imparts to the rake structure a true orbalanced drivetorque. A balanced torque drive in the sense of thisinvention comprises amain or bull gear at the top of the rotarystructure, a source of motor power, and torque transmitting meanswhereby interbalanced shares of the motor torque are applied equally ata plurality of points along the periphery of the'main gear. In this wayeach point of torque application on the main gear receives its equalshare of the motor torque so that there is imparted to the rakestructure as a whole a mechanically efiicient true driving torque at alltimes.

' Also this invention relates to improvements in overload responsivemeans for indicating overloads encoun-.

teredby the rake structure.

One object is to provide balanced torque drive'means which are simpleand dependable, as well as structurally highly adaptable in that theyshould readily lend themselves to apply interbalanced shares of drivingtorques at two or at more than two points of torque application alongthe periphery of the main gear.

That object according to this invention-is attainable in a drivemechanism which comprises a torque-responsive yieldable member for eachpoint of torque application and in which the respective yieldablemembers are operatively interconnected by a hydraulic pipe pressuresystem to restrain, and hydraulically interbalance the torque reactionsof these members.

Another object is to provide simple and dependable means for indicatingoverload conditions affecting the rake structure. That object'isattained by providing pressure responsive means governed by thefluidpressure' of the hydraulic interbalancing system, whereby excessivepressure in the balancing system is employed is the criterion ofoverload.

In one embodiment the drive mechanism ofeach-of the torque-responsivemembers is in the form of a wormshaft which is axially yieldable whileexerting its torque reaction force.

More specifically, although in" no limiting sense, that embodiment ishere illustrated in connection with the' rotary rake structure of the'type'th'at is supported upon,

2,931,241" Patented Apr. 5, 1960- this platform an hydraulic pressurepipe system opera-- tively interconnecting the respectivetorque-responsive wormshafts in a manner to restrain their respectiveyielding. movements while interbalancing the respective axial torquereaction forces exerted by these shafts.

In summary, this invention provides drive mechanism for engaging themain gear of the rotary rake structure at a plurality of points oftorque application, which mechanism includes for each point of torqueapplication a torque-responsive yieldable member, with the addition of ahydraulic pressure pipe system operatively interconnecting all thetorquerrespo'nsive members in a manner to hydraulically interbalance therespective torque-reaction forces exerted by these members.

In the drawings:

Figure 1 is a semi-diagrammatical vertical sectional view of whichcertain type of settling tank with rake drive mechanism having axiallyyieldable wormshafts representing the torque responsive elements andalso indicating the hydraulic pressure pipe system for interbalancingthe wormshafts.

Figure 2 is an enlarged detail plan view taken on line 2.-2 of. Figure 1of the drive mechanism.

Figure 3 is a further enlarged sectional view taken on me 3'3 of thedrive mechanism of Figure.2.

Figure 4 is a greatly enlargeddetail view of one of the limit switchboxes associated with the respective torque v responsive wormshafts, forautomatically providing makeup fluid for the hydraulic pressure system.

Figure 5 is a top view, with box cover removed, of the limit switchdevice of Figure 4.

In the semi-diagrammatic Figure 1, there is shown, by way of example, asettling tank of the type in which a center pier supports the rotarystructure as well as the mechanism for rotating the rake structure. Thetank 10 comprises a shallow conical bottom 11, a cylindrical wall 12, aperipheral overflow launder 13 with annular scum bafiie 14. The bottomhas a sludge discharge sump 15 near a center pier 16 which is hollow andinto which leads a feed infiuent 17 below the tank bottom. Feedsuspension rises in the hollow pier to discharge from the top endthereof radially in all directions as through feed openings 18.

The pier 16 is surrounded by, and providessupport fora rake structure 19as well as for driving mechanism 20 The pier is topped by a platformstructure 21 providing" annular bearing means for the rake structure 19and more specifically for an internal bull gear indicated at 22.. Therotary rake structure thus comprises the'bull gear 22,11"

central cage structure 23 rigidly connected to the bull,

defined by internal bull gear 22, and it also carries the hydraulic pipesystem indicated at 28 which is for the purpose of hydraulicallyinterbalancing the torque reaction forces arising from the respectivepoints of torque application at the bull gear 22 as will be described indetail further. below.

In the enlarged detail Figures 2 and 3, a cast-iron stationary platformstructure 29 fixed atop a center pier lndlcated at 30, supports anannular ball bearing 31 which carries rotatable thereon an internal bullgear 32 constituting the top end portion of a rotary rake structureindicated at 33.

The platform structure 29 also carries a drive mechanism M for impartingtorque to the internal bull gear 32 at a plurality of points of torqueapplication T, T, and T The drive mechanism M is here shown to comprisea plurality of three identical worm drive units 34*,34 and 34" mountedon the platform structure 29, each having a pinion 35 35 and 35respectively engaging the bull gear 32 at the respective points oftorque application T, T and T Each of the drive pinions is rigidly andconcentrically connected to a worm gear 36, 36 and 36 respectively,which worm gears are driven by wormshafts 37 37 and 37 Each of thesewormshafts has what is herein termed a free or protruding end portion 7p and p respectively carrying fixed thereon a sprocket 38 38" and 38respectively whereby the wormshafts are driven simultaneously from asingle counter shaft 39 also mounted on the platform structure 29 as inhorizontal bearings 40, 41 and 42. That is to say, the counter shaft 39has fixed thereon a set of sprockets 43, 44, and 45 driving thesprockets 38 38 and 38 respectively through chains indicated at 46, 47and 48 respectively. A motor 49 drives the counter shaft 39 as through achain element 50 or other suitable power transmitting drive element.

The opposite end of each wormshaft herein termed the encased ends q q;,and g respectively, is surrounded by a housing portion in which it isallowed to exert its axial thrust reaction against a body of hydraulicpressure fluid confined in an hydraulic pressure pipe system common toall three wormshafts, so that the torque reaction forces or thrustreactions of the three wormshafts are in fact interbalanced through thisfluid body and thus equalized at all times during the operation of themechanism. This hydraulic interbalance insures that equal shares of themotor torque are thus applied at the respective points of torqueapplication T, T and T on the bull gear 32.

The interbalancing hydraulic system as indicated in Figure 2 is in theform of a pipe system S containing the hydraulic fluid, operatively byinterconnecting the encased ends q q and q of the respective wormshaftsin a manner described in detail further below.

The worm drive units 34, 34 and 34 are identical so that only one ofthem, for instance the unit 34 need here be described in further detail.

The worm drive unit 34 comprises the aforementioned pinion 35, worm gear36*, and wormshaft 37 Pinion 35 has a vertical pinion shaft 51 the upperend of which has fixed thereon the worm gear 36*. The pinion shaft 51,rotates in a lower thrust bearing 52 and an upper guide bearing 53. Bothbearings 52 and 53 are mounted in a gear housing 54 comprising a lowersection 55 and an upper section 56. The lower housing section 55contaming the pinion 35 with the lower bearing 52, constitutes a pocketformed by the platform structure 29 itself The upper housing section 56containing the upper bear ng 53 as well as the worm gear 36 andwormshaft 37*- 1s fastened as by flange connection 57 to the top of theplatform structure 29.

Since all three wormshafts 37 37 and 37 are operatively connected to thehydraulic pressure pipe system S in the identical manner, namely by wayof their respective encased end portions q g and q it will suflice hereto refer to detail Figures, 4 and in de c i ing this relationship asexemplified by wormshaft 37" of worm drive unit 34.

In detail Figures 4 and 5 the encased end portion q; of wormshaft 37rotates in a combination transverse and thrust bearing 58 contained in acylindrical or pistonshaped member herein briefly termed the piston 59which is sealingly slidable horizontally within a cylindrical housingportion 60 that is part of the upper gear housing section 56 andhorizontally protruding therefrom. However,-this potential axial slidingmovement of the wormshaft is limited to a distance d due to the factthat the outer end of the piston member 59 has a protrusion 61 lodgingin a recess 62 formed in the surrounding cylindrical portion 60. Thepiston 59 thus forms with the surrounding cylindrical portion 60 ahydraulic pressure pipe system S.

Hence, if the pipe system S is properly supplied with hydraulic fluid tothe extent of filling the respective hydraulic chambers 63 and forcingthe respective pistons 59 into their most retracted position within therecess 62, and if drive motor torque is applied to the drive mechanism,each point of torque application T, T and T at the bull gear .32 willreceive its equal share of the driving torque because of the hydraulicinterbalance through pipe system S of the thrust reaction forces exertedby the respective wormshafts 37 37, 37 in the directions indicated byarrows A, B and C (see Fig. 2).

In connection with the hydraulic interbalancing system S there are herealso provided devices for automatically supplying make-up fluid to thatsystem. That is to say, loss or leakage of hydraulic fluid from the pipesystem S will result in a corresponding axial displacement of thewormshafts in the direction of the thrust reactions A, B and C (see Fig.2), even though without necessarily disturbing the existing hydraulicinterbalance itself.

When this axial displacement of the wormshatts reaches a predetermineddegree, a contact carrier or finger 64 being unitary with the piston 59closes a limit switch 66 to start a pump-motor unit 67 (see Fig. 2). Atthe rate at which make-up fluid thus enters the pipe system S, the axialdisplacement of the wormshafts will be corrected as the shafts are beingforced back in the direction of thrust arrow D (see Fig. 4) until finger64 actuates an opposite limit switch 68 to stop the pump motor. Thelimit switches 66 and 68 are mounted in a switch box 69 rising from thehorizontal housing portion 60, and provided with a box cover 70. Suchswitch box in the plan view of Figure 2 is shown to overlie therespective encased end portions q q; and q of the respective wormshafts37 37 and 37.

,At 0 there is diagrammatically indicated an overload responsive devicethat will react to an excessive rise in the pressure of the fluid in thehydraulic balancing system S. That is to say, in case the rake structurein the tank should encounter an excessive sludge load, such overloadwill manifest itself in a corresponding rise in pressure of thehydraulic fluid that is trapped in the interbalancing system S.

When that condition develops, the overload-responsive device willfunction automatically to sound an alarm or to stop the drive motor 49,or to do both. The overload responsive function may be such as to soundan alarm and to stop the motor sequentially or simultaneously.

It is to be understood that this invention need not be limited to themechanism as embodied in the center pier type of settling tank hereinshown. For instance, the invention may also be embodied in a drivemechanism in which the torque-responsive yieldable elements are otherthan the axially yieldable wormshafts herein shown.

Still another embodiment would be in a mechanism in which the bull gearitself is in the form of a worm gear, and the torque-responsive driveelements are represented by a plurality of wormshafts directly engagingthis bull gear at the respective points of torque application thereof; Asuitable application ofthat embodiment is in the type of settling tank'in which. the rotary raking structure and its drive mechanism aresupported from an overhead structure spanning the tank. In that.instance, the rotary rake structure may comprise a vertical, solid ortubular shaft, the top end of which has fixed thereto a gear to whichthe driving torgue is applied at a plurality of points.

Furthermore, the invention is not limited to the points of torqueapplications T, T and T of the embodiment shown, inasmuch as there maybeonly two such points diametrically opposite to one another, or elseeven more than three such points equidistantly spaced with respect toone another.

As this invention may be embodied in several forms without departingfrom the spirit of essential characteristicsthereof, the presentembodiment is therefore illustrative and not restrictive, since thescope of the invention is defined by the appended claims rather'than bythe description preceding them, and all changes that fall within themetes and bounds of the claims, or equivalents of such metes and bounds,are therefore intended to be embraced by the claims.

I claim:

1. Drive mechanism for a rotary structure turntable about a verticalaxis upon an annular thrust bearing mounted upon a supporting frame,such as the rotary rake structure of a center pier type sedimentationtank where the rake has a centralrcage portion rotatably supported uponand surrounding the center pier, and the mechanism is mounted .upon saidframe supported by said pier, which mechanism comprises an internallytoothed bull gear provided at the top end of the cage portion forrotating the rake structure, a plurality of trains of torquetransmitting elements, disposed within the space substantially definedby the area of said bull gear, said trains terminating at their outerends in drive pinions having driving engagements with said bull gear, atorque imparting motor with torque distributing means for impartingpositive drive torque to each said train, and means for interbalancingsaid drive torques imparted to said trains to attain substantially a netbalanced drive torque effective upon the bull gear; characterizedthereby that each said train comprises a torque-responsive yieldablemember exerting a thrust reaction when the mechanism is in operation,with the addition of a hydraulic pressure communicating pipe systemcontaining a fluid pressure-propagating medium, operativelyinterconnecting said torque-responsive members to exert upon theminterbalanced restraining forces simultaneously through said fluidmedium thereby interbalancing the torque reaction forces exerted by saidyieldable members, which system comprises intercommunicating pressurebranch pipes leading to the respective torque-responsive members, and acommunicating chamber at the outer end of each branch pipe andoperatively associated with a respective torque-responsive member andbeing expandable in opposition to the torque reaction force thereof,each said train comprises a worm drive for each respective drive pinion,which worm drive has a hous ing and a horizontal worm shaft representingsaid respective torque-responsive member and having a driven end and afree end, and in which said expandable member comprises a cylinderconstituting part of said housing and a hollow piston having provided inthe hollow thereof combined transverse and thrust-bearing means for saidfree end of the worm shaft.

2. Drive mechanism according to claim 1, in which said pluralitycomprises three trains of torque transmitting elements, each traincomprising a worm drive to each respective drive pinion, which wormdrive has a horizontal wormshaft representing said torque-responsivemember and having a driven end and a free end, said free end havingoperatively associated therewith said communicating chamber, and inwhich said; torque disa:

tributing means comprise a master shaft mountedorr said frame to extendparallel to said worm shafts and. positive rotation transmitting meansbetween said master shaft and each driven end of the said worm shaft.

3. Drive mechanism for a rotary structure supportedby a frame, whichstructure has a bull gear for rotating the same, and has associatedtherewith a plurality of torque transmitting drive pinions engaging saidbull gear,- at a plurality of points of simultaneous torque applica-:tion, said points of application being substantially evenly. spaced withrespect to one another along the periphery of said bull gear, a drivemotor and torque distributing'i gear train means for imparting positivedrive torquesimultaneously to said drive pinions, characterized there:by that each said train comprises a torque-responsive yieldable member,with the additionof a hydraulicv pres-- sure pipe system containing apressure propagating. fluid medium, operatively interconnecting saidtorqu e-respon sive members to provide interbalanced restraining forcesthrough said medium simultaneously upon said yieldable members therebyinterbalancing the' torque reaction'forces exerted by said yieldablemembers, said system comprising intercommunicating pressure branch pipesleading to the respective torque-responsive members-and a com municatingpressure chamber at the end of each' branclr pipe and operativelyassociated with a torque-responsive member and being expandableinopposition to the torque reaction force thereof, said system includingmeans re sponsive to predetermined movement of saidyieldable.

- membersto supply saidsystemwith additional fiuidmc'a dium.

4. In a multi-drive transmission the combination which comprises aplurality of gear trains each having a worm gear mounted on an inputshaft and an intermediate reduction gear train driven by said worm gear,drive means driving said input shafts, a single bull gear driven by saidplurality of reduction gear trains, a plurality of cylinders, aplurality of pistons slidable in each said cylinder, bearing meansmounting one end of each said shafts for rotation relative to anassociated piston and against relative axial movement, and a hydraulicpressure system operatively associated with each said cylinder wherebyeach said worm gear through fluid medium in said system is yieldablyintermeshed with its associated gear reduction train and all said wormgears and reduction train are intermeshed under equal pressure.

5. In combination with a transmission comprising a plurality of geartrains, each said gear train having an input gear, an intermediatereduction gear and a single output gear, a driven shaft carrying eachsaid input gear, single drive means driving said input shafts transverseand thrust-bearing means interconnecting each said shaft with a piston,said piston slidable within a cylinder, a hydraulic fluid pressuresystem operatively associated with each said cylinder, means responsiveto predetermined movement of said pistons to supply said system withadditional fluid under pressure, and hydraulic pressure responsiveoverload means responsive to the hydraulic pressure of said system tocut oif said drive means.

6. In a multi-drive transmission the combination which comprises, aplurality of gear trains each having a worm gear mounted on an inputshaft and an intermediate reduction gear train driven by said worm gear;drive means driving said input shaft; a single bull gear driven by saidplurality of reduction gear trains; a plurality of cylinders; aplurality of pistons slideable in each of said cylinders; transverse andthrust bearing means mounting one end of said shaft for rotationrelative to an associated piston and against axial movement relativethereto so that said shaft and piston will axially move together,wherein at least said transverse bearing means are anti-friction bearingmeans; and a hydraulic pressure system operatively associated with eachof said cylinders whereby each 7 said worm gear through fluid medium insaid system is yieldably intermeshed with its associated gear reductiontrain and all said worm gears and reduction trains are intermeshed underequal pressure.

7. In a multi-drive transmission the combination which comprises, aplurality of gear trains each having a worm gear mounted on an inputshaft and an intermediate reduction gear train driven by said worm gear;drive means driving said input shaft; a single bull gear driven by saidplurality of reduction gear trains; a plurality of cylinders; aplurality of pistons slideable in said cylinder at least one of whichpistons has an actuating portion extending laterally therefrom; meansmounting one end of said shaft for rotation relative to an associatedpiston and against axial movement relative thereto so that said shaftand piston will axially move together; a hydraulic pressure systemoperatively associated with each of said cylinders whereby each, saidworm gear through fiuid pressure medium in saidsystem is yieldablyintermeshed with its associated gear reduction train and all said wormgears and reduction train are intermeshed under equal pressure; andmeans actuated by the actuating portion of said piston to start thesupply of additional fluid medium to said system in response topredetermined axial movement of said piston in one direction, and tostop the supply in response to predetermined movement in the oppositedirection.

. 8; In a multi-drive transmission the combination which comprises, aplurality of gear trains each having a worm gear mounted on an inputshaft and reduction gear train driven by said worm gear; drive meansdriving said input shaft; a single bullv gear drivc'n by said pluralityof reduction gear trains; a' plurality of cylinders; a plurality ofpistons slideahle in said cylinders; bearing means mounting one end ofsaid shaft for rotation relative to an associated piston and againstaxial movement relative thereto so that said shaft and piston willaxially move together; a hydraulic pressure system operativelyassociated with each of said cylinders whereby each said worm gearthrough fluid pressure medium in said system is yieldably intermeshedwith its associated gear reduction train and all said worm gears andreduction trains are intermeshed under equal pressure; and meansactuated by said piston to supply additional fluid pressure medium tosaid system comprising a first limit switch actuated by said piston forstarting the supply in response to predetermined axial movement of saidsystem in one direction, and a second limit switch actuated by saidpiston for stopping the supply in response to predetermined axialmovement of said piston in the opposite direction.

References Cited in the file of this patent UNITED STATES PATENTS1,458,131 Davis June 12, 1923 2,322,719 Scott June 22, 1943 2,386,367Taylor Oct. 9, 1945 2,496,857 Cronstedt Feb. 7, 1950 2,518,708 MooreAug. 15, 1950 2,563,622 Scott Aug. 7, 1951 FOREIGN PATENTS 4,748Australia Oct. 31, 1931

